Speed control of 3 phase induction motor

hi guys,im new to tis forum
currently im doin a project bout design a cicuit to control the speed of a 3 phase induction motor, i already hav the inverter circuit, but im having a problem to get the firing circuit.do anyone have a sample for this?really thank you if can give me a hand here...

Of course there are other ways. But they are far more complicated and less reliable than using a microprocessor. You could, for example, gang together a control to simultaneously vary both motor supply voltage and the frequency from a VCO. It would be quite challenging to design and adjust, though. You would have to do a lot more soldering, too. In the long run, it would probably be more expensive as well. And less reliable. But you could do it.